Japanese quail eggs were subjected to 2.45 GHz CW microwave radiation at 5 mW/cm squared (SAR = 4.03 mWg) during the first 12 days of embryogeny and reared to 22 weeks of age before examination. Humoral immune potential, as indicated by comparable anti-CRBC antibody, IgM and IgG, levels at 0, 4 and 7 days post-immunization in both exposed and control quail, was not affected significantly. However, cell mediated immune potential measured by the reaction to intradermal injection of phytohemagglutinin-P in the wing web, was reduced in the exposed females, but not in the exposed males. Additionally, total leucocyte numbers and absolute circulating numbers of lymphocytes, monocytes and heterophils were increased significantly only in the exposed females. Mice were irradiated at 2.45 GHz for 8 hours per day at a power density of 30 mW/cm squared during days 1-6 and 6-15 of pregnancy. Samples were obtained on day 17 of pregnancy. The total white blood cell and differential cell counts of peripheral blood samples were not affected by either exposure regimen. No effect was noted on either the erythroid or myeloid mitotic indexes of bone marrow samples.